The present invention for measuring the rate of flow of liquids in conduits.
It is known to measure the rate of flow of liquids in conduits by having two spaced apart detection means outside the conduit which can detect discontinuities in the liquid flowing through the conduit. The discontinuities can be bubbles, solid impurities and other areas of different phase to the bulk liquid. Using conventional detection methods, such as measuring capacitance, or other electrical properties, using ultra-sonic or short wavelength radiation, etc., the pattern of the discontinuities can be continuously measured and plotted at each location. The plot of the discontinuities at each location are then correlated electronically and this is used to measure the time taken for the discontinuities to pass sequentially to the two detectors, this measures the flow rate of the discontinuities and hence the flow rate of the liquid. Although the method involves assumptions about the uniform nature and flow rate of the discontinuities, in practice it can give a useful measurement of the flow rate of the liquid.
We have now devised an improved method of measuring the flow rate of liquids in conduits and equipment for measuring the flow rate of liquids in conduits.
According to the invention there is provided a method for measuring the flow rate of a fluid in a conduit, which method comprises placing within the flowing fluid a detector unit which comprises two linearly spaced apart detectors which have a shielding unit made from an electrically conductive material positioned between them, but not in electrical contact with them, and which have a shielding unit made from an electrically conductive material upstream and downstream of the detectors and adjacent, but not in electrical contact with them, which method comprises applying an electrical field between the detector unit and the wall of the conduit and measuring variations in the electrical field by means of the detectors and, by correlating discontinuities in the electrical field, measuring the flow rate of the fluid.
The invention also provides a device for measuring the flow rate of fluids in a conduit which device is adapted to fit within the conduit and comprises two spaced apart detector means capable of detecting and measuring an electric field, which detector means have positioned between them and either side of them, but not in electrical contact with them, shielding units made from an electrically conductive material, the shielding units being in electrical contact with each other and the detector means being connected to a measuring means able to measure variations in the electrical field between the conduit wall and the device, there being means to apply an electrical field between the detector unit and the wall of the conduit.
By correlating the variations in the electric field, as measured by the detector means, between the device and the wall of the conduit the speed of flow of the bulk fluid can be measured.